// Copyright (c) 2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/strings/utf_string_conversion_utils.h"

#include "base/third_party/icu/icu_utf.h"

namespace base {

// ReadUnicodeCharacter --------------------------------------------------------

bool ReadUnicodeCharacter(const char* src,
    int32_t src_len,
    int32_t* char_index,
    uint32_t* code_point_out)
{
    // U8_NEXT expects to be able to use -1 to signal an error, so we must
    // use a signed type for code_point.  But this function returns false
    // on error anyway, so code_point_out is unsigned.
    int32_t code_point;
    CBU8_NEXT(src, *char_index, src_len, code_point);
    *code_point_out = static_cast<uint32_t>(code_point);

    // The ICU macro above moves to the next char, we want to point to the last
    // char consumed.
    (*char_index)--;

    // Validate the decoded value.
    return IsValidCodepoint(code_point);
}

bool ReadUnicodeCharacter(const char16* src,
    int32_t src_len,
    int32_t* char_index,
    uint32_t* code_point)
{
    if (CBU16_IS_SURROGATE(src[*char_index])) {
        if (!CBU16_IS_SURROGATE_LEAD(src[*char_index]) || *char_index + 1 >= src_len || !CBU16_IS_TRAIL(src[*char_index + 1])) {
            // Invalid surrogate pair.
            return false;
        }

        // Valid surrogate pair.
        *code_point = CBU16_GET_SUPPLEMENTARY(src[*char_index],
            src[*char_index + 1]);
        (*char_index)++;
    } else {
        // Not a surrogate, just one 16-bit word.
        *code_point = src[*char_index];
    }

    return IsValidCodepoint(*code_point);
}

#if defined(WCHAR_T_IS_UTF32)
bool ReadUnicodeCharacter(const wchar_t* src,
    int32_t src_len,
    int32_t* char_index,
    uint32_t* code_point)
{
    // Conversion is easy since the source is 32-bit.
    *code_point = src[*char_index];

    // Validate the value.
    return IsValidCodepoint(*code_point);
}
#endif // defined(WCHAR_T_IS_UTF32)

// WriteUnicodeCharacter -------------------------------------------------------

size_t WriteUnicodeCharacter(uint32_t code_point, std::string* output)
{
    if (code_point <= 0x7f) {
        // Fast path the common case of one byte.
        output->push_back(static_cast<char>(code_point));
        return 1;
    }

    // CBU8_APPEND_UNSAFE can append up to 4 bytes.
    size_t char_offset = output->length();
    size_t original_char_offset = char_offset;
    output->resize(char_offset + CBU8_MAX_LENGTH);

    CBU8_APPEND_UNSAFE(&(*output)[0], char_offset, code_point);

    // CBU8_APPEND_UNSAFE will advance our pointer past the inserted character, so
    // it will represent the new length of the string.
    output->resize(char_offset);
    return char_offset - original_char_offset;
}

size_t WriteUnicodeCharacter(uint32_t code_point, string16* output)
{
    if (CBU16_LENGTH(code_point) == 1) {
        // Thie code point is in the Basic Multilingual Plane (BMP).
        output->push_back(static_cast<char16>(code_point));
        return 1;
    }
    // Non-BMP characters use a double-character encoding.
    size_t char_offset = output->length();
    output->resize(char_offset + CBU16_MAX_LENGTH);
    CBU16_APPEND_UNSAFE(&(*output)[0], char_offset, code_point);
    return CBU16_MAX_LENGTH;
}

// Generalized Unicode converter -----------------------------------------------

template <typename CHAR>
void PrepareForUTF8Output(const CHAR* src,
    size_t src_len,
    std::string* output)
{
    output->clear();
    if (src_len == 0)
        return;
    if (src[0] < 0x80) {
        // Assume that the entire input will be ASCII.
        output->reserve(src_len);
    } else {
        // Assume that the entire input is non-ASCII and will have 3 bytes per char.
        output->reserve(src_len * 3);
    }
}

// Instantiate versions we know callers will need.
template void PrepareForUTF8Output(const wchar_t*, size_t, std::string*);
#if !defined(WIN32)
template void PrepareForUTF8Output(const char16*, size_t, std::string*);
#endif

template <typename STRING>
void PrepareForUTF16Or32Output(const char* src,
    size_t src_len,
    STRING* output)
{
    output->clear();
    if (src_len == 0)
        return;
    if (static_cast<unsigned char>(src[0]) < 0x80) {
        // Assume the input is all ASCII, which means 1:1 correspondence.
        output->reserve(src_len);
    } else {
        // Otherwise assume that the UTF-8 sequences will have 2 bytes for each
        // character.
        output->reserve(src_len / 2);
    }
}

// Instantiate versions we know callers will need.

template void PrepareForUTF16Or32Output(const char*, size_t, std::wstring*);
#if !defined(WIN32)
template void PrepareForUTF16Or32Output(const char*, size_t, string16*);
#endif

} // namespace base
